The present invention relates to a broadband communication device. More particularly, the present invention provides a broadband silicon nitride polarization beam splitter with low loss and high extinction ratio for entire C-band.
Over the last few decades, the use of broadband communication networks exploded. In the early days Internet, popular applications were limited to emails, bulletin board, and mostly informational and text-based web page surfing, and the amount of data transferred was usually relatively small. Today, Internet and mobile applications demand a huge amount of bandwidth for transferring photo, video, music, and other multimedia files. For example, a social network like Facebook processes more than 500 TB of data daily. With such high demands on data and data transfer, existing data communication systems need to be improved to address these needs.
As an important integrated optics device, a compact polarization beam splitter (PBS) can be used to achieve polarization independent operation of photonic integrated circuits (PICs) and linear optical quantum information technology. A perfect PBS should simultaneously have short device length, high extinction ratios, low insertion loss, broadband operation, stability, simple structure and high fabrication tolerances. The state-of-art designs for the PBS are mostly based on asymmetrical Mach-Zehnder interferometer (MZI), single directional coupler, Multimode interferometer (MMI), or surface plasmons waveguide. Although immense amount of concrete researches have been done, few perfect PBS has been reported and most of the designs mentioned above are either low in extinction ratio, difficult to manufacture, or wavelength-sensitive in C-band.
Therefore, it is desired to develop improved polarization beam splitter with high extinction ratio and low insertion loss over broad communication band.